A state report issued Tuesday confirms that the disaster-struck Crandall Canyon Mine had planned to operate by pulling out pillars of coal, the controversial technique termed "retreat mining."

Coal output of the mine could drop by 300,000 short tons this year because of the tragedy, which has left six miners missing and three rescuers dead.

However, the production drop is a small blip in the overall Utah mining picture, says the report by the Utah Geological Survey, "Annual Review and Forecast of Utah Coal Production and Distribution — 2006."

The report projected, "Current plans call for pulling pillars with one continuous miner (machine) in the Hiawatha seam of the Crandall Canyon mine for the next few years, producing about 625,000 short tons in 2007 and 586,000 tons in 2008."

That information was based on an interview with the mine operators in February, said the report's author, Michael D. Vanden Berg. He said he is unaware of any change in the plan between then and the time of the mine disaster on Aug. 6.

The report notes that in 2006, the Utah coal industry was booming, extending a strong recovery from a slump in 2004. Last year, production from coal mines amounted to 26.1 million short tons, up 6.4 percent over the 2005 level. This year's production was estimated at 26.4 million tons, despite the fact that work was halted at three mines.

One of the idled mines is the South Crandall Mine, on the same property as the Crandall Canyon Mine.

The sister mines dig into different coal seams, said Vanden Berg. Both mines are owned by UtahAmerican Energy Inc.-Murray Energy Corp.

"In August of 2006, Murray Energy Corp., the largest independent, family-owned coal producer in the United States, acquired ANDALEX Resources and its four subsidiary companies," the report says. "These properties are the Tower Division, made up of the Aberdeen and Pinnacle mines; GENWAL Resources Inc., which manages the Crandall Canyon and South Crandall Canyon mines; West Ridge Resources Inc., which manages the West Ridge Mine; and the Wildcat Loadout, based in Carbon County."

The report says retreat mining in the Pinnacle Mine produced only 8,000 tons before the mine was indefinitely idled in January 2006. A loadout is a coal-loading facility.

UtahAmerican Energy is a subsidiary of Murray Energy, the report adds. GENWAL and West Ridge are owned half by Murray and half by the Intermountain Power Agency, it says.